With the advent of new network applications and services, end users are demanding high bandwidth end-to-end connections that have to be provisioned automatically and dynamically.
A transport network can comprise multiple network domains. Different carriers or service providers may wish to manage their own parts of the network, thereby creating different network domains. In addition, an operator may wish to divide their network into domains managed independently from each other for reasons such as scalability, geographical position, and multi-vendor interoperability.
The main standardisation bodies, such as Internet Engineering Task Force (IETF), Optical Internetworking Forum (OIF) and International Telecommunications Union (ITU), are addressing aspects of routing in a multi-domain/multi-technology scenario.
One proposal is a “per domain” approach. In this scheme, the entry border node of each domain involved in a path computation requests its domain Path Computation Element (PCE) for a path inside that domain. The resulting end-to-end path is a concatenation of those paths where each domain PCE computes the relative multi-domain segment that crosses the domain itself. This approach is not efficient because the path determined as optimal by a domain may be not optimal for the neighbour.
Another proposal is called Backward Recursive Path Computation (BRPC). This scheme assumes that the PCEs of the domains collaborate to create a Virtual Shortest Path Tree. The Virtual Shortest Path Tree comprises all possible end-to-end paths crossing the sequence domain starting from destination to the source. In this way, the source has the list of all possible end-to-end paths and can select the best according to a specific metric.
Another proposal is called Hierarchical Path Computation Element (H-PCE), described in IETF Request for Comments document 6805 (RFC 6805). Unlike the other approaches, H-PCE does not require a-priori knowledge of the sequence of the domains. H-PCE is based on two levels of PCE that have a hierarchical relationship. A Child Path Computation Element (C-PCE) knows topology information of a domain and is responsible for computing and providing connections inside the domain. A Parent Path Computation Element (P-PCE) is responsible for determining the sequence of domains and coordinates the C-PCEs involved in the end-to-end (E2E) connection.
Most efforts to date have been directed towards routing of Point-to-Point (P2P) services. There is increasing interest in Point-to-Multipoint (P2MP) services, i.e. services with a single source and multiple destination points. With the advent of datacenter and cloud applications, multicast services are increasingly in demand, especially for high-capacity applications such as multicast Virtual Private Networks (VPN) and Internet Protocol Television (IPTV).
The present invention seeks to facilitate routing of Point-to-Multipoint (P2MP) services in a multi-domain network.